Fixes handle()-related strict warnings such as "Strict Standards:
Declaration of AdminPanelAction::handle() should be compatible with
Action::handle()"
Ref. #190
clientError and serverError exit after they're done so no need for
break or return. Also, $this->format is default.
We also got rid of the incredibly verbose version of $this->isPost()
which was spread all over the place.
Not all of this cleaning up is done yet.
L10n/i18n updates.
Superfluous whitespace removed.
Add FIXME for a few i18n issues I couldn't solve this quickly.
Takes care of documentation for all core code added in merge of "people tags" feature (Commit:e75c9988ebe33822e493ac225859bc593ff9b855).